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Best ASHP manufacturer/model for new passive house


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Hi

Treated floor area m² is 189.1 m2

Heating demand kWh/(m²a) 17

Heating load W/m² 10

Not sure of the hot water usage - 2 adults and a child but the house is flexible enough to provide accom for 4 adults and a child down the line

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6 minutes ago, markharro said:

Not sure of the hot water usage - 2 adults and a child but the house is flexible enough to provide accom for 4 adults and a child down the line


So put either a 400 litre UVC in, or a pair of 200 slimline in tandem. 

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I had wondered about a 300 litre and then for the "annexe" part of the house which is where (potentially) another 2 adults could be housed, an electric shower and potentially an electric instant hot water solution for the washhandbasin and hot water for the kitchenette there. The thinking being that it may only be used sporadically and even if it is then we are hoping to put in a 9kW solar PV system that may power it directly during daytime use?

But anyway back to what I was asking - any leading manufacturers of the main ASHP unit?

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My sap EPC said 5kWh for 2.9 people for DHW.  But two of us are using nearer an average of 7kWh.

 

Looks like you only need a 2kW heat source for heating.

 

Have you thought about UFH with Willis heater and direct electric water heating through E7.  2x 3kW Willis heaters (1 duty one standby) some isolation valves, circa £200 in parts.  Low capital spend compared to heat pump.

 

Direct E7 heating with PV diverter contribution.

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1 hour ago, markharro said:

Heating demand kWh/(m²a) 17

 

So not actually a certified Passive House then.... ?

 

In which case, I'd avoid the list from the passivehouse database, it looks very unrepresentative of what's generally available in the UK, and likely paying premium for a PH certificate on a project that doesn't require it.

Even if you're planning a certified PH, getting a certified ASHP doesn't help at all unless you're going for the higher (net zero) "plus" or "premium" ratings. A standard PH doesn't care what the heat source is - you could be burning newborn kittens and still be awarded the certificate.

 

Edited by joth
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Yes it is to be a certified PH! I didn't understand that I needed a PH certified ASHP for a certified standard PH but I think you have confirmed that I don't in your answer! That's just as well as I am not familiar with the majority of the products on the certified list 

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13 minutes ago, markharro said:

Yes it is to be a certified PH! I didn't understand that I needed a PH certified ASHP for a certified standard PH but I think you have confirmed that I don't in your answer! That's just as well as I am not familiar with the majority of the products on the certified list 

 

We built a (certified) Enerphit Plus passive house, and didn't use a certified heat pump. With respect to getting our project certification, I really don't think there was any issue with using a non-certified heatpump. For a vanilla (not plus) PH I'd pay no attention to that list.

 

However you need to do something about your heating demand.  17 kWh/(m²a)  is 13% over the passive house limit of 15.
https://passiv.de/en/02_informations/02_passive-house-requirements/02_passive-house-requirements.htm

 

 

Edited by joth
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@joth It's 15 kWh/sqm heating demand or 10W/sqm peak demand. So tight, but it is a pass.  You are right you don't need a certified anything for PH certification, apart from MVHR that is.  Even for Plus/Premium you don't need a certified ASHP, although a better COP does help with your PER score which may or may not be important depending on how much PV you have.

 

You only need a small ASHP with those numbers. You do need to consider DHW reheat times though and/or look at non-traditional approches for DHW to workaround this.

 

We have heating demand of 10W/m and around 30m2 treated floor area.  We are using the 7kW aroTherm Plus which is more than enough for heating/coolig and we probably could have used th 5kw.

 

Looks like the PH databse heat-pumps are only the all-in-one ashp/ventilation units, not standard monoblocs.

 

 

Edited by Dan F
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8 hours ago, markharro said:

had wondered about a 300 litre and then for the "annexe" part of the house which is where (potentially) another 2 adults could be housed, an electric shower and potentially an electric instant hot water solution for the washhandbasin and hot water for the kitchenette there. The thinking being that it may only be used sporadically and even if it is then we are hoping to put in a 9kW solar PV system that may power it directly during daytime use?


Why..??? Just go with a pair of 200 UVCs, one place, one system. Use them as the dump loads for the PV and then only switch the second one on when you have guests or it’s in use. It’s a 3 way lever valve and a switch to put it into the circuit. You will never power a 10kw electric shower from a 9kW solar array unless they shower at 12 noon ..! 

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1 hour ago, PeterW said:

You will never power a 10kw electric shower from a 9kW solar array unless they shower at 12 noon ..! 

No, but you may reduce the grid draw by whatever the PV is generating, but why would you fit a piddling, pathetic, cheap, instantaneous electric shower.

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I have a similar conundrum. Renovating to EnerPHit standard with a heat load in PHPP of 25w/m2 and a treated area of 72m2 giving a total load of 1800W. We are a family of two adults and two small kids. 

 

The most seemingly reputable company I'm speaking with have quoted me a 5KW Vaillant Arotherm Plus together with 40w buffer tank and 300L water tank. The more I look into this the more this seems overspecified, especially since Vaillant have a 3.5KW model. I am a bit worried however that even this would be overkill and lead to an inefficient setup. 

 

I've read about the difference between fixed and inverter driven heat pumps and the fact that in my situation I should be looking for an inverter driven one so it can run at below max output allowing constant (and therefore efficient) operation more of the time, avoiding short cycling. But I can't see anything on the Vaillant website to suggest it has a variable output. Is this variability just a given these days, hence it's not mentioned or is it a helpful differentiating factor? 

 

On 31/05/2022 at 12:54, JohnMo said:

Have you thought about UFH with Willis heater and direct electric water heating through E7.  2x 3kW Willis heaters (1 duty one standby) some isolation valves, circa £200 in parts.  Low capital spend compared to heat pump.

This is an interesting alternative approach. It would certainly be nice not to have a big heat pump in our small garden. @JohnMocan you give any guidance on where I could helpfully read up on a setup like this? 

 

 

Edited by AndyRP
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There is plenty of info on this site with reference Willis heaters, it would be best to look around and have a good read.  I find the easiest way to find stuff is search through google.

 

https://www.google.co.uk/search?q=buildhub+willis+heater+site:forum.buildhub.org.uk&sxsrf=ALiCzsZxamojBzYQRLlAn3-Hb_saXJJJJg:1654722699811&sa=X&ved=2ahUKEwiF9uS14p74AhWVolwKHe94AiwQrQIoBHoECAkQBQ&biw=1253&bih=608&dpr=1

 

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48 minutes ago, markharro said:

What are the pros and cons of the different refrigerants you see mentioned? 

Environmental usually.

Though CO2 HPs can deliver a higher temperatures. Higher temperature is not more energy. 

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